In ophthalmology, the technique of using a photosensitizer and electromagnetic radiation to change the biomechanical and biochemical properties of tissue, in particular the cornea, for therapeutic purposes has been known for more than 10 years.
The human eyeball is bounded by the corneosclera. Due to internal eye pressure, the corneosclera, which contains collagen, has an approximately spherical shape. In the posterior eyeball region, the corneosclera consists of white sclera. The cornea, which is transparent to visible light, is situated in the anterior region.
Deformations of the corneosclera can cause ametropia. For example, axial myopia, a type of myopia, can result from a sclera longitudinal expansion of the eyeball. An ellipsoidal shaped corneal surface can cause a form of astigmatism or other high order aberration, which is also called “irregular corneal curvature”. Another defect of the cornea is keratoconus, in which a pathological softening of the cornea leads to a progressive thinning and cone-shaped deformation of the cornea. As the bulging increases, the cornea becomes thinner below the center. It can fracture and become scarred, which can permanently reduce visual acuity.
In known techniques, the corneal epithelium is at least partially removed to introduce riboflavin into the cornea, because the epithelium hinders the riboflavin from penetrating the cornea by acting as a barrier to the diffusion of the riboflavin molecules into the cornea. The removal of the epithelium is, however, usually painful for the patient and the subsequent healing process may have complications.